This invention relates to a filter or catalyst body comprising wires or fibers which are constructed in one or several layers as a woven cloth, braiding (netting or mesh) or knitted fabric, with the wires or fibers being at least partially connected to one another by sintering or welding.
Filters and catalyst bodies consisting of several layers or plies of woven cloths, braiding or knitted fabrics made from metal fibers or metal wires which have been sintered together, are already known.
Filters of this type are used as socalled drop base filters, with the separation of the medium to be filtered occurring on the surfaces of the multilayer woven cloth, braiding or knitted fabric, or its constituents. The efficiency of the filter is limited by the available surface.
Such filters may also be used as catalysts, e.g. for cleaning exhaust gases from internal combustion engines in motor vehicles. Here too, the largest possible surfaces are required to allow an exchange of electrons to occur.
Catalytically effective materials, such as platinum, rhodium or vanadium, for example, are accordingly used as catalysts.
Soot filters for diesel engines, which are usually made of ceramic material, are also known. The hot engine exhaust gases are conveyed through the ceramic filter body, and in the porous channels together with the prevailing higher temperatures, the soot, i.e. carbon, is converted in the filter walls of the filter body into gas and ash. Apart from ceramic filter bodies, filter bodies made of other filter materials, such as sintered materials made from metal, have also been previously proposed.
However the known filters and catalysts have the disadvantage that their separation surfaces are limited. For this reason a relatively large number of layers of woven cloths or knitted fabrics are required, with it being possible for the thicknesses to be between a few millimeters and several meters according to each case.
In the prior West German application P 39 08 581.3 a process for the manufacture of a catalyst body and a catalyst, in which powdery or granular particles are sintered onto the individual layers or their components, has already been proposed.
In this way, a multiple surface enlargement is achieved, with which a much higher absorption surface and, consequently, a considerably larger filter surface becomes available. Thus, a clear reduction in size of the filter is obtained with the same filter capacity or a clearly higher filter capacity, is achieved with the same size of filter.
The object of the invention is to improve even further a filter or catalyst body of this type with respect to its efficiency and, in particular, its filter capacity.